67656721 has 8 divisors (see below), whose sum is σ = 74340000. Its totient is φ = 61062240.

The previous prime is 67656713. The next prime is 67656749. The reversal of 67656721 is 12765676.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 67656721 - 2³ = 67656713 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (67656751) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20596 + ... + 23653.

It is an arithmetic number, because the mean of its divisors is an integer number (9292500).

Almost surely, 2^67656721 is an apocalyptic number.

It is an amenable number.

67656721 is a deficient number, since it is larger than the sum of its proper divisors (6683279).

67656721 is a wasteful number, since it uses less digits than its factorization.

67656721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44399.

The product of its digits is 105840, while the sum is 40.

The square root of 67656721 is about 8225.3705691598. The cubic root of 67656721 is about 407.4775146613.

The spelling of 67656721 in words is "sixty-seven million, six hundred fifty-six thousand, seven hundred twenty-one".